Hello Mike.
Thank you for your help. A said that arduino is reading weird things because i measured the output of the opamp with a multimeter and i get.. 200mV. When i put this output into the A0 of my Arduino, i get big diferents values oscillating The Schematic Image is attached. I have a sensor representated by the transistor, then a conditioning circuitry. The output comes from an opamp and all devices has the same GND with the sources. What i am doing is to wire the output to the A0 input pin and the Gnd of the circuit to the GND pin of my Arduino.I am wondering if the problem comes from impedances coupling or something else that i cant see :(.
Thank you again.
Dgarizado.
